ScienceDaily (Feb. 1, 2010) - New research is casting doubt on the old
adage, "All you need to run is a pair of shoes."
Scientists have found that those who run barefoot, or in minimal footwear,
tend to avoid "heel-striking," and instead land on the ball of the foot or
the middle of the foot. In so doing, these runners use the architecture of
the foot and leg and some clever Newtonian physics to avoid hurtful and
potentially damaging impacts, equivalent to two to three times body weight,
that shod heel-strikers repeatedly experience.
"People who don't wear shoes when they run have an astonishingly different
strike," says Daniel E. Lieberman, professor of human evolutionary biology
at Harvard University and co-author of a paper appearing this week in the
journal Nature. "By landing on the middle or front of the foot, barefoot
runners have almost no impact collision, much less than most shod runners
generate when they heel-strike. Most people today think barefoot running is
dangerous and hurts, but actually you can run barefoot on the world's
hardest surfaces without the slightest discomfort and pain. All you need is
a few calluses to avoid roughing up the skin of the foot. Further, it might
be less injurious than the way some people run in shoes."
Working with populations of runners in the United States and Kenya,
Lieberman and his colleagues at Harvard, the University of Glasgow, and Moi
University looked at the running gaits of three groups: those who had always
run barefoot, those who had always worn shoes, and those who had converted
to barefoot running from shod running. The researchers found a striking
pattern.
Most shod runners -- more than 75 percent of Americans -- heel-strike,
experiencing a very large and sudden collision force about 1,000 times per
mile run. People who run barefoot, however, tend to land with a springy step
towards the middle or front of the foot.
"Heel-striking is painful when barefoot or in minimal shoes because it
causes a large collisional force each time a foot lands on the ground," says
co-author Madhusudhan Venkadesan, a postdoctoral researcher in applied
mathematics and human evolutionary biology at Harvard. "Barefoot runners
point their toes more at landing, avoiding this collision by decreasing the
effective mass of the foot that comes to a sudden stop when you land, and by
having a more compliant, or springy, leg."
The differences between shod and unshod running have evolutionary
underpinnings. For example, says Lieberman, our early Australopith ancestors
had less developed arches in their feet. Homo sapiens, by contrast, has
evolved a strong, large arch that we use as a spring when running.
"Our feet were made in part for running," Lieberman says. But as he and his
co-authors write in Nature: "Humans have engaged in endurance running for
millions of years, but the modern running shoe was not invented until the
1970s. For most of human evolutionary history, runners were either barefoot
or wore minimal footwear such as sandals or moccasins with smaller heels and
little cushioning."
For modern humans who have grown up wearing shoes, barefoot or minimal shoe
running is something to be eased into, warns Lieberman. Modern running shoes
are designed to make heel-striking easy and comfortable. The padded heel
cushions the force of the impact, making heel-striking less punishing.
"Running barefoot or in minimal shoes is fun but uses different muscles,"
says Lieberman. "If you've been a heel-striker all your life you have to
transition slowly to build strength in your calf and foot muscles."
In the future, he hopes, the kind of work done in this paper can not only
investigate barefoot running, but can provide insight into how to better
prevent the repetitive stress injuries that afflict a high percentage of
runners today.
"Our hope is that an evolutionary medicine approach to running and sports
injury can help people run better for longer and feel better while they do
it," says Lieberman, who has created a web site,
www.barefootrunning.fas.harvard.edu, to educate runners about the respective
merits of shod and barefoot running.
The Nature paper arose out of the senior honors theses of two Harvard
undergraduates, William A. Werbel '08 and Adam E. Daoud '09, both of whom
went to Africa with Lieberman to help collect data for this study.
Lieberman's co-authors on the Nature paper are Venkadesan and Daoud at
Harvard; Werbel, now at the University of Michigan; Susan D'Andrea of the
Providence Veterans Affairs Medical Center in Providence, R.I.; Irene S.
Davis of the University of Delaware; and Robert Ojiambo Mang'Eni and Yannis
Pitsiladis of Moi University in Kenya and the University of Glasgow in
Scotland.
The research was funded by the American School of Prehistoric Research, the
Goelet Fund, Harvard University, and Vibram USA.
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